Two methods for the measurement are specified: Method A (Ball displacement method): Determination of the viscosity of a pitch at a given temperature determined using a sample of pitch having similar characteristics by measurement of the time a ball, drawn by a defined force, requires to traverse a fixed distance within a measuring tube filled with the sample of molten pitch. Method B (Rotation of a cylindrical body method): Measurement of the shear stress of a substance at a selected rotational speed at a given temperature by means of a system composed of a cylindrical-conical body revolving in the substance contained in a cylindrical vessel.